19
Glossary
Beam Non-Uniformity Ration –
By nature, an ultrasound beam is not homogeneous. The BNR is a ratio of
the highest intensity found in the beam field to the average intensity as indicated on the output display of
the unit. This measure may not exceed 6.0:1. Because of the areas of increased intensity, the sound head is
moved continuously during the treatment.
Continuous Mode –
The output of the ultrasound is not interrupted during the treatment time. This mode
imparts the most energy to the tissues and is used when a maximal effect is desired.
(See Duty Cycle)
Coupling Media –
An agent used to insure that the ultrasound is transmitted from the sound head to the tis-
sue to be treated. Gels or lotions labeled for therapeutic ultrasound use is recommended.
Duty Cycle –
This is the ratio of the “On” time to “Total” time of the cycle, expressed as a percentage. The duty
cycle describes the burst-on time in the Russian Waveform and the pulsed modes of ultrasound. The lower
the percentage, the lower temporal average intensity. 100% is continuous
ultrasound.
Effective Radiating Area (ERA) –
A measure of the ultrasound beam made underwater, 5 mm from the radi-
ating surface of the sound head. The ERA is always smaller than the geometric area of the sound head, but
should be as close as possible. This measurement is used to calculate the ultrasound intensity in W/cm
2
.
Frequency –
Selectable to 1 or 3.3 MHz with the 5 cm
2
or 2 cm
2
sound head. The lower the frequency, the
longer the wavelength, the deeper the penetration of ultrasound.
Lead Zirconate Titanate –
A synthetic crystal used to create the ultrasound beam by vibrating 1,000,000
(1 MHz) to 3,300,000 (3.3 MHz) times per second. This type of crystal is both durable and efficient in its
functions.
Power –
A measure of the intensity of the ultrasound delivered to the patient. Unit of measure is watts (W) or
w/cm
2
.
Pulse Duration –
Refers to the amount of time the ultrasound is being delivered in the pulsed mode. For
example, in the 20% Duty Cycle mode, the ultrasound is delivered for 2 msec and off for 8 msec throughout
the treatment period.
Pulsed Mode –
The output of the ultrasound is automatically interrupted during the treatment time. This
limits the amount of energy delivered to the tissues.
Sound Head (Applicator) –
The applicator used for delivery of ultrasound to the patient. An aluminum face
contracts the patient’s skin. It covers a transducer mechanism that converts electrical energy to mechanical
energy in the form of a vibrating crystal.
Ultrasound Intensity –
Ultrasound power delivered to the patient expressed in total power as watts (W) or in
terms of the sound head’s effective radiating area, watts per centimeter squared (W/cm
2
).
